Here is the homework question... According to the Guinness Book of World Records, the highest rotary speed ever attained was 2010m/s(4500mph). The rotating rod was 15.3cm(6in.) long. Assume the speed quoted is that of the end of the rod. What is the centripetal acceleration of the end of the rod? So I think since they say rotary speed they are talking about angular velocity here. so i would say angular velocity (w) = 2010m/s. Is this correct? or is it tangential velocity (v) = 2010m/s? okay....does this mean it's rotating about the middle or about the end? (diameter being 15.3 radius being 7.65) orrrrrr (radius being 15.3 and diameter being 30.6) ??